Over the last few decades, the electronics industry has undergone a revolution by the use of semiconductor technology to fabricate small, highly integrated electronic regions. The most common semiconductor technology presently used is silicon-based. A large variety of semiconductor devices have been manufactured having various applications in numerous disciplines. Such silicon-based semiconductor devices often include metal-oxide-semiconductor (MOS) transistors, complimentary MOS (CMOS) transistors, bipolar transistors, BiCMOS transistors, etc.
Each of these semiconductor devices generally include a semiconductor substrate on which a number of transistors are formed. The particular structure of a given transistor can vary between transistor types. For example, MOS transistors generally include source and drain regions and a gate electrode which modulates current between the source and drain regions. Bipolar transistors generally include a base a collector, and an emitter. In addition to the active regions (e.g., source regions, drain regions, gate electrodes, bases, emitters, collectors, etc.) of the transistors, both bipolar and MOS transistors often include polysilicon lines, active regions which typically run over regions of the substrate, such as field oxide regions, and interconnect various portions of the region.
The various active regions on a semiconductor device are typically interconnected by metal lines. In most cases, a silicide is formed over some or all of the active regions in order to facilitate contact between the active regions and subsequent metal lines. The silicide areas also serve to reduce the sheet resistance of the active regions. Silicide areas are typically formed by depositing a layer of metal, such as tungsten, cobalt or titanium, over the substrate and annealing the wafer, typically in a two-step process. During the annealing process, the deposited metal reacts with underlying silicon and forms a metal silicidation layer.
It is typically desirable to minimize the resistivity of the silicide areas. The resistivity of the silicide areas generally depends upon the temperature at which the silicide reaction occurs as well as the type of metal used to form the silicide areas. Generally, the temperature of the reaction is a first order variable in the resultant resistivity. Higher silicide reaction temperatures result in silicide areas having lower resistivity. In conventional silicidation techniques, using elevated temperatures can however result in the formation of deleterious silicide stringers, which in some instances can extend between the silicide areas of adjacent active regions and electrically couple the active regions.